1. Field of the Invention
The present invention relates to non-invasive ventilation and pressure support systems, and, in particular, to a patient interface device that may be used with such system to deliver gas to a patient that includes an exhaust gas assembly for reducing noise caused by patient exhalation and/or diffusing the patient exhalation flow.
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube in their esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver positive airway pressure (PAP) therapy to treat certain medical disorders, the most notable of which is obstructive sleep apnea (OSA). Known PAP therapies include continuous positive airway pressure (CPAP), wherein a constant positive pressure is provided to the airway of the patient in order to splint open the patient's airway, and variable airway pressure, wherein the pressure provided to the airway of the patient is varied with the patient's respiratory cycle. Such therapies are typically provided to the patient at night while the patient is sleeping.
Non-invasive ventilation and pressure support therapies as just described involve the placement of a patient interface device including a mask component typically having a soft, flexible cushion on the face of a patient. The mask component may be, without limitation, a nasal mask that seals around the patient's nose, a nasal cushion having nasal prongs that are received within the patient's nares, a nasal/oral mask that seals over the nose and mouth, or a total face mask that seals around the patient's face. Such patient interface devices may also employ other patient contacting components, such as forehead supports, cheek pads and chin pads.
The patient interface device is connected to a gas delivery hose and interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient. It is known to maintain such devices on the face of a wearer by a headgear having one or more straps adapted to fit over/around the patient's head.
Such patient interface devices also include an exhaust gas assembly for exhausting a flow of gas from the patient interface device and/or gas delivery hose to the ambient atmosphere. This is necessary to flush the patient's exhaled CO2 from the mask and/or gas delivery hose. While numerous different configurations for such exhaust gas assemblies are known, conventional exhaust gas assemblies can suffer excessive noise as the flow of exhaust gas passes through the exhaust gas assembly. This noise is undesirable in that it may disturb the sleep of the patient or the patient's bed partner.
Another problem associated with conventional exhaust gas assemblies is that stream of gas exiting the exhaust gas assembly can disturb the patient or the patient's bed partner. For example, the stream of gas, if directed into the eyes, or other sensitive part of the patient or the patient's bed partner can be annoying and/or uncomfortable.